Subminiature potentiometer



Feb. 15, 1966 D. J. BAKER 3,235,825

SUBMINIATURE POTENTIOMETER Filed Oct. 16. 1961 INVENTOR. DONALD J. BAKERFlas. 7@

United States Patent 3,235,828 SUBMINIATURE POTENTIOMETER Donald J.Baker, 938-D th St, Santa Monica, Calif. Filed Oct. 16, 1961, Ser. No.145,203

14 Claims. (Cl. 3381'74) This invention relates to potentiometers andmore particularly to an improved subminiature device characterized bynumerous unique features including the capability of being compactlystacked without interfering with the adjustment of any individualdevices. The potentiometers of this invention are also characterized bythe small number of individual components, the ease, speed andpositiveness of operation of the adjusting means, simplicity ofassembly, reliability of the product and other features pointed outbelow.

The subminiature potentiometer of this invention features a housingformed in two parts each of which is provided on its interior with acentral boss having complementally-shaped opposed surfaces coacting witha pair of contactor components to hold the latter in assembled positionwhile permitting at least one of the contactor components to rotatealong and in contact with the wire wound resistance component of thepotentiometer. An additional and important feature of the rotatingcontact element is that it is quickly adjusted to a new position bymeans of an improved adjuster utilizing an annular driven element infirm driving contact with a rotary adjusting element journaled in thecasing wall and provided on its exposed outer end with a tool engagingsurface. Other features include an annular resistance component designedto have a snug frictional fit with a receiving groove formed in one ofthe casing halves and a rotary contact member arranged to be held inexcellent electrical contact with the resistance winding by reason ofthe resilience of the contractor finger itself and additionally by theresilience of a spring washer secured to one terminal lead andinterposed between one of the casing bosses and the rotary contactor.Another important feature of the present invention resides in the factthat the mating halves of the casing have aligned channels formed indiametrically opposed portions of their rim edges. One of these passagesis designed to seat the three terminal leads which extend from directconnections to internal parts of the potentiometer to the exterior ofthe casing. The other pasage is formed to seat snugly the reducedcentral portion of the adjustable member driving the rotary contractor.The inner end of this adjusting member is provided with serrations orteeth designed to bite into and form a firm driving contact with thedriven ring member fixed to the rotary contactor. Desirably, portions ofthe exterior peripheral side walls of the casing through which thedescribed passages open are cut away or relieved in a manner describedbelow to permit compact stacking of the potentiometers without, however,interfering with access to the individual adjusting members of eachdevice.

Another unique feature of the present design is the fact that theadjusting screw for the resistance element is arranged to rotate aboutan axis at right angles to the axis of rotation of the rotary contactormember. This feature, coupled with the fact that adjusting member isprovided with a relatively large diameter pinion having drivingengagement with a driven ring mounted on the radial face of the rotarycontact member, has the very distinct advantage over prior potentiometeradjusting means that it permits adjustment throughout the full range ofthe potentiometer with only a relatively few complete turns of theadjusting member.

It is therefore a primary object of the present invention to provide animproved subminiature potentiometer characterized by its simplicity,ruggedness, reliability,

pactness, limited number of components, and the mutually cooperatingnature of the components with one another to the end that they are heldpositively assembled in relatively movable operating arrangement withoutfasteners of any nature.

Another object of the invention is the provision of a fully enclosedsubminiature potentiometer having rotary adjusting means accessible fromthe exterior and operable to drive the adjusting contactor throughoutits range of movement with a minimum number of rotations of theadjusting member.

Another object of the invention is the provision of a compact,inexpensive potentiometer having diagonally opposed corners cut away toprovide surfaces through one of which the terminal wires project andthrough the other of which the rotary adjuster member projects therebypermitting the potentiometers to be stacked in immediate proximity toone another without interfering with access to the individual adjustmentmeans for each device.

These and other more specific objects will appear upon reading thefollowing specification and claims and upon considering in connectiontherewith the attached drawings to which they relate.

Referring now to the drawings in which a preferred embodiment of theinvention is illustrated.

FIGURE 1 is a top plan view showing a plurality of potentiometersconstructed according to this invention in one preferred stackingarrangement in close proximity to one another;

FIGURE 2 is an enlarged plan view of an individual potentiometer;

FIGURE 3 is a cross-sectional View taken along line 3-3 on FIGURE 2 andon a still larger scale and many times larger than the actual commercialsize of the devices;

FIGURE 4 is a plan view of the lower casing half and of all componentsin their assembled position immediately prior to the assembly of thecasing cover, the view being taken generally along line 44 on FIGURE 3;and

FIGURE 5 is a fragmentary cross-sectional view taken along line 55 onFIGURE 4.

Referring more particularly to FIGURES 2 to 5, there is shown asubminiature potentiometer designated generally 10 and embodying thenovel features and principles of the present invention. The enclosingcasing of the potentiometer is preferably formed from a suitablenonconductive material capable of being molded to high tolerance valuesand not subject to distortion or deformation under a wide range ofadverse conditions normally encountered in manufacture and usage. Thiscasing is molded to form two halves including a lower half 11 and anupper half or cover 12. Both halves have con tinuous facing rim surfacesparallel to the respective exterior bottom surfaces. Lower half 11 hasan upstanding peripheral wall provided with a flat upper surface 13against which the mating surface 14 of cover 12 seats. Desirably, cover12. is sealed closed against surface 13 of lower half 11 by epoxy orother suitable adhesive not soluble in water.

Both casing half 11 and cover 12 are provided centrally of theirinteriors with respective circular posts or bosses 16 and 17 havingimportant mutually cooperating functions. The opposed ends of eachinclude comple mentally-shaped interfitting surfaces, lower boss 16being formed with a semi-spherical depression 18 receiving therewithinthe spherical surface of a boss 19 carried by overlying boss 17. Thespacing between the opposed surfaces depression 18 and extension 19approximates the thickness of the shallow cup-shaped rotary contactor 20held rotatably socketed between these members.

Contactor 20 is preferably stamped from thin resilient material havingexcellent electrical properties and so as to embrace the upper end ofboss 16 loosely for smooth rotation about this boss. The annularradially disposed lip 22 of contactor 20 has firmly bonded to its uppersurface a continuous ring 23 of suitable plastic or elastomeric materialand is preferably formed with a frusto-conical upper surface 24 forfrictional driving contact with a rotary adjusting device to bedescribed presently. The center of contactor 20 is formed with asemi-spherical socket 25 conforming with the shape of the recess 18 andthe overlying extension 19. It is also pointed out that the radial rim22 of contactor 20 has a pair of radial slits 27 providing a contactfinger 28 which projects radially beyond the rim edge of the contactorand is depressed somewhat below the plane of rim 22, as is best shown inFIGURE 3. Contact finger 28 of the rotary contact member 20 hasresilient pressure contact with a helical winding of resistance wire 39carried by an annular core 31. The resistance unit formed by winding 30and core 31 has a snug fit within an annular channel 33 molded intocasing half 11 concentrically of boss 16.

The opposite ends of resistance 30 are welded, brazed or otherwiseelectrically secured to a pair of insulated terminal leads 35, 36 whichextend downwardly into the lower casing half 11 through a well 38opening at its bottom into annular groove 33 in the manner best shown inFIGURES 3 and 4. A third insulated terminal lead 39 is brazed orotherwise secured to a tab" 40 integral with a dished spring washer 42seated about the base of extension 19 integral with boss 17 of casingcover 12. Tab 40 is generally L-shaped and has its longer or verticalleg lying against the side wall of boss 17 and its horizontal legsecured to the inner end of terminal lead 39.

The three terminal leads 35, 36 and 39 extend from the interior of thecasing through a radial passage 44 formed partially in lower casing 11and partially in cover 12. The cross-sectional size and shape of passage44 is preferably no greater than that required snugly to accommodateleads 35, 36 and 39 when firmly compacted together. Desirably, the sidewalls of passage 44 have one or more integral sharp-edged projectionsextending into the passage and adapted to bite into the insulation ofthe terminal Wires thereby firmly anchoring them against axial movementalong passage 44.

Axially aligned with passage 44 and located on the diagonally oppositeside of the potentiometer casing is a semi-circular passage 47 likewiseformed partly in lower casing member 11 and partly in cover 12. Passage47 forms a cylindrical journal for the reduced midsection 48 of theadjustable driving member for rotary contactor 20. The corners of thecasing and cover through which passage 47 opens is cut away to provide aflat surface 49 against which the enlarged outer end 50 of member 48rests. Head 50 is preferably provided with a slot 51 to receive a screwdriver or like tool for rotating adjuster 48, the enlarged inner end ofadjuster 48 being provided with a beveled pinion-like member havingsharp-edged teeth 53 which bite into surface 24 of the resilient ring23. These teeth or serrations are highly effective in rotating contactor20 in a direction depending upon the direction of rotation of adjuster48. Preferably, passage 47 seating the adjuster is provided at its outerend with an annular recess seating a resilient packing gasket 54.

It is to be understood that the corner of the potentiometer casingthrough which terminal lead passage 44 opens is preferably cut away toprovide an exterior surface 59 similar to surface 49 on the diagonallyopposite corner of the potentiometer. The significance of thisarrangement will be best understood be reference to FIG- URE 1 showing aplurality of identical potentiometers 10 arranged in two parallel rowswith their adjacent peripheral edges in direct contact with one another.The potentiorneters are so arranged that the cut away corners providedwith surfaces 59 of a group of four potentiometers cooperate with oneanother to provide a well 60 accom modating' terminal leads 35, 36 and39. Well 60 is of adequate size to accommodate the terminal leads ofadjoining columns of stacked potentiometers which may be firmly securedin place by the use of suitable fasteners extending through another pairof diagonally opposed cutaway corners 62,

Also to be observed from FIGURE 1 is the fact that when thepotentiometers of this invention are compactly stacked and secured inplace, as thereshown, the outer ends 50 of the adjuster member 48 of theindividual potentiometers are exposed and freely accessible to atechnicians adjusting tool. It will therefore be understood that anydesired number of the potentiometers may be arranged in two adjacentrows and stacked to any required height without posing a problem so faras the terminal leads are concerned or, more particularly, as respectsaccessibility of each potentiometer for individual adjustment.

The mode of assembling the described potentiometer will be quiteapparent from the foregoing description of its components. It will beunderstood that the terminal leads are secured to the opposite ends ofthe resistance winding and to tab 40 of spring washer 42 prior to theassembly of the components into the casing. Desirably, these leads aresufficiently long as to permit their connection directly to a terminalboard or to the components in circuit therewith. The assembler placeslower casing member 11 face up and inserts the resistance unit intogroove 33 and presses lead wires 35 and 36 firmly down into the lowerhalf of passage 44. Contactor unit 20 is then socketed in the sphericaldepression 25 and the third terminal lead 39 and the attached springwasher and contactor are then centeredover contactor 20. The next stepis to assemble the reduced midportion of the one piece adjuster 48 intothe lower half of passage 47. The final assembly operation comprisesapplying a thin coating of adhesive to surface 14 of cover member 12,care being exercised to avoid having adhesive contact the sur-- face ofpassage 47. However, adhesive is applied about the portion of the leadwires passing through passage 44. The cover is then inserted so as toseat spherical extension 19 in the complementally-shaped socket 25 ofcontactor 20. In this connection, care is taken to have boss 19 passthrough the opening in the center of spring contactor 42. The cover isthen pressed tightly against the juxtaposed rim surface 13 of the lowercasing half and held in this position until the adhesive takes a set. Itwill be understood that the pressure assembly of the cover serves todeform or stress the washer-like spring contactor 42 thereby assuring afirm electrical contact between this washer and the surfaces 'ofcontactor 20.

From the foregoing it will be apparent that no fastener devices of anykind are employed in connection with any subassembly and that the entireassembly operation is performed without need for tools of any kind.

After assembly and connection to the equipment with which thepotentiometer is to be used, the technician may apply a tool to slot 51of adjuster element 48 and rotate: it in either direction causing thesharp edges of pinion 52 to engage the surface of the driven element 23and to rotate contactor 20 to adjust spring finger 28 to a des1redposition along the exposed surface of winding 30. As will be readilyapparent from FIGURES 3 and 5 a single rotation of adjuster 48 serves tomove contact finger 28 along a major fraction of the full length of theresistance winding. For this reason, the full adjustment of thepotentiometer is accomplished throrrgh an unusually low number ofrotations of adjuster 48.

In closing it is desired to point out that an appreciation of thecompactness of the present potentiometer when manufactured tosubminiature scale is to be gained from the fact that more than fifty ofthe described potentiometers may be installed Within one cubic inch ofspace. When so stacked in accordance with the principles disclosedabove, the rotary adjuster of each is exposed and accessible forindividual adjustment.

While the particular subminiature potentiometer herein shown anddisclosed in detail is fully capable of attaining the objects andproviding the advantages hereinbefore stated, it is to be understoodthat it is merely illustrative of the presently preferred embodiments ofthe invention and that no limitations are intended to the details ofconstruction or design herein shown other than as defined in theappended claims.

I claim:

1. A subminiature potentiometer comprising a twopart Wafer-like hollowcasing of insulating material having a pair of opposed bosses integralwith and extending toward one another from a pair of opposed interiorwalls thereof and positioned centrally of and cooperating with interiorsurfaces of said hollow casing to provide a surrounding endless channel,a wire-Wound ring-like resistive unit seated in said endless channel,rotary conducting contactor means having a contactor supported forrotary movement directly on and between said opposed bosses with itscontactor bearing against the winding of said resistive unit, thejuxtaposed surfaces of said contactor means and of said opposed bossesbeing complemental to one another and shaped to permit said contactormeans to rotate while holding said contactor means against displacementradially of its axis of rotation, said rotary contactor means beingshaped complementally to juxtaposed surfaces of said pair of bosses soas to be held rotatably centered therebetween, separate electricalconductors electrically connected respectively with said rotarycontactor and with the opposite ends of said resistive unit and havingterminal ends extending to the exterior of said hollow casing, and meansadjustable from the exterior of one edge of said wafer-like casing andoperatively connected with said contactor means for adjusting theposition of said contactor along the winding of said resistive unit.

2. A subminiature potentiometer comprising a twopart casing of generallycup-shaped non-conductive parts having mating rim edges engaged with oneanother and provided centrally of the interior bottom portion of eachwith an imperforate integral boss projecting toward and terminatingclosely adjacent one another and cooperating with interior surfaces ofsaid casing parts to form a surrounding annular chamber, a unitarywire-wound resistive unit in said annular chamber having terminal leadsextending to the exterior of said casing as a group between the matingrim edges thereof and electrically connnected with the opposite ends ofsaid resistive unit, unitary conducting contactor means held captivelycentered between the adjacent ends of said bosses for rotary movementthereabout and including conducting means in contact with the Winding onsaid resistive unit, a one-piece adjusting member mounted in said casingwith its inner end in rotary driving relationship to said unitaryconducting contactor means and having an outer end accessible foradjustment from the exterior of said casing, and third terminal leadmeans extending from an electrical connection with said unitaryconducting contactor means to the exterior of said casing.

3. A subminiature potentiometer as defined in claim 2 characterized inthat the central area of said unitary contactor means is shapedcomplementally to juxtaposed surfaces of at least one of said opposedbosses whereby said contactor means is held rotatably in assembledrelation between said bosses and free for relative rotary movement aboutthe axis of said opposed bosses.

4. A subminiature potentiometer as defined in claim 3 characterized inthat said unitary contactor means includes an annular drive ring fixedthereto and engaged with a toothed inner end portion on said one-pieceadjusting member.

5. A subminiature potentiometer as defined in claim 3 characterized inthat said adjusting member is rotatable about an axis normal to the axisof rotation of said unitary contactor means and projects from saidcasing in general alignment with and on the opposite side of said casingfrom the place of exit of said group of terminal leads.

6. A subminiature potentiometer as defined in claim 5 characterized inthat said adjusting member is held assembled to said casing between thefacing rim edges of the cup-shaped halves thereof.

7. A subminiature potentiometer as defined in claim 3 characterized inthat said casing halves are bounded along the exterior side wallsthereof by four walls merging at cut-away corners, two of said opposedcorners being adapted to receive mounting fastener means for securingsaid potentiometer fixedly in a place of use, and the remaining opposedcut-away corners serving respectively as the place of exit of theterminal leads and as the place of exit of said one-piece adjustingmember for said unitary conducting contactor means.

8. A subminiature potentiometer comprising a waferlike casing havingexterior peripheral side walls arranged generally at right angles to oneanother, two diagonally opposed corners of said casing being cut away toform end faces extending between the adjacent side Walls defining saidopposed corners, an adjustable resistive assembly supported interiorlyof said casing having rotary means extending outwardly through one ofsaid cutaway corners of said casing with its axis of rotation extendingcrosswise of said casing and intersecting said two diagonally opposedcorners and accessible exteriorly of the casing to adjust said resistiveassembly, and terminal means for said resistive assembly extendingoutwardly through the other of said diagonally opposed cut-away cornerswhereby a plurality of said potentiometers can be compactly arrangededge to edge in a planar ring with the outer ends of said rotaryadjusting means outermost and readily accessible for adjustmentnotwithstanding the compact arrangement of said casings and with theterminal means of the respective potentiometers grouped togetherdiametrically opposite the rotary adjusting means of the associatedpotentiometer and centrally of the ring of potentiometers.

9. A subminiature potentiometer comprising a pair of shallow casingmembers of nonconductive material each having an upstanding opposed bosscentrally thereof having their ends terminating closely adjacent oneanother in the assembled position of said casing members, the rim edgesof said casing members being assembled in contact with one another, ashallow annular groove encircling at least one of said bosses, anannular wire-wound resistive element in said groove, rotary contactormeans overlying said resistive element and supported for rotaryadjustment about the axes and directly between the closely spacedadjacent ends of said bosses, said contactor means having rotary drivemeans therefor journaled in a radial passage opening through the rimedges of said casing members transversely of said contacting rim edgesand held assembled by said casing members, said rotary drive meanshaving an inner end in driving engagement with said rotary contactormeans and being rotatable about an axis intersecting the axis ofrotation of said rotary contactor means, and terminal wires electricallyconnected to said resistive element and to said rotary contactor means.

10. A potentiometer as defined in claim 9 characterized in that theportion of said rotary contactor means in driving engagement with saidrotary drive means comprises a ring member having a radius substantiallyless than the radius of said resistive element whereby a relatively fewturns of said rotary drive means sufiices to move said contactor meansalong the full length of said resistive element.

11. A potentiometer as defined in claim 9 characterized in that saidrotary contactor means includes a ring of resilient material having itsexposed surface in high friction driving contact with the inner end ofsaid rotary drive means.

12. A potentiometer as defined in claim 9 characterized in that saidcasing is provided with a passage opening into the interface between thecontacting rim edges of said casing members, said terminal wiresextending to the exterior of said casing through said passage, saidpassage including sharp edged ribs projecting from the passage walls andeffective to bite into said terminal wires in the assembled position ofthe casing members to anchor said terminal wires against movementaxially of said passage.

13. A subminiature potentiometer comprising a waferlike casing moldedfrom insulating material and comprising a generally cup-shaped lowerhalf having a first boss projecting upwardly from the center of itsbottom wall, a cover half engaging the rim edges of said bottom half andhaving a second boss projecting downwardly from its center, said secondboss having an end surface shaped complementally to the juxtaposed endof said first boss, a rotary contactor ring journalled between theclosely-spaced complementally shaped ends of said first and secondbosses and held captive therebetween in the assembled position of saidcasing halves, a wire-wound annular resistor element encircling saidfirst boss and secured in place in the bottom of said lower casing half,said contactor ring having a contact finger thereon positioned to bearagainst said wire-wound resistor, resilient conducting ring meansencirclingsaid second boss and bearing against said rotary contactorring, rotary means held captive in mating recesses formed between therim edges of said casing halves adjustable from the exterior of saidwafer-like casing and having driving engagement with said rotarycontactor ring and effective to rotate the latter in either directionabout the aligned axes of said first and second bosses, and terminalwires extending to the exterior of said casing from the opposite ends ofsaid wire-wound resistor and from said resilient conducting ring means.

14. A potentiometer as defined in claim 13 charac terized in that thejuxtaposed ends of said first and second bosses are providedrespectively with a depression and a complementally shaped projectionextending into said depression and cooperating therewith and with theinter- Vening complementally shaped portion of said contactor ring tohold the latter captive but free for rotation between the inner ends ofsaid first and second bosses.

References Cited by the Examiner RICHARD M. WOOD, Primary Examiner.

1. A SUBMINIATURE POTENTIOMETER COMPRISING A TWOPART WAFER-LIKE HOLLOW CASING OF INSULATING MATERIAL HAVING A PAIR OF OPPOSED BOSSES INTEGRAL WITH AND EXTENDING TOWARD ONE ANOTHER FROM A PAIR OF OPPOSED INTERIOR WALLS THEREOF AND POSITIONED CENTRALLY OF AND COOPERATING WITH INTERIOR SURFACES OF SAID HOLLOW CASING TO PROVIDE A SURROUNDING ENDLES CHANNEL, A WIRE-WOUND RING-LIKE RESISTIVE UNIT SEATED IN SAID ENDLESS CHANNEL, ROTARY CONDUCTING CONTACTOR MEANS HAVING A CONTACTOR SUPPORTED FOR ROTARY MOVEMENT DIRECTLY ON AND BETWEEN SAID OPPOSED BOSSED WITH ITS CONTACTOR BEARING AGAINST THE WINDING OF SAID RESISTIVE UNIT, THE JUXTAPOSED SURFACES OF SAID CONTACTOR MEANS AND OF SAID OPPOSED BOSSES BEING COMPLEMENTAL TO ONE ANOTHER AND SHAPED TO PERMIT SAID CONTACTOR MEANS TO ROTATE WHILE HOLDING SAID CONTACTOR MEANS AGAINST DISPLACEMENT RADIALLY OF ITS AXIS OF ROTATION, SAID ROTARY CONTACTOR MEANS BEING SHAPED COMPLEMENTALLY TO JUXTAPOSED SURFACES OF SAID PAIR OF BOSSES SO AS TO BE HELD ROTATABLY CENTERED THEREBETWEEN, SEPARATE ELECTRICAL CONDUCTORS ELECTRICALLY CONNECTED RESPECTIVELY WITH SAID ROTARY CONTACTOR AND WITH THE OPPOSITE ENDS OF SAID RESISTIVE UNIT AND HAVING TERMINAL ENDS EXTENDING TO THE EXTERIOR OF SAID HOLLOW CASING, AND MEANS ADJUSTABLE FROM THE EXTERIOR OF ONE EDGE OF SAID WAFER-LIKE CASING AND OPERATIVELY CONNECTED WITH SAID CONTACTOR MEANS FOR ADJUSTING THE POSITION OF SAID CONTACTOR ALONG THE WINDING OF SAID RESISTIVE UNIT. 